US3509502A - Electromagnetic relay structure - Google Patents

Description

April 28, 1970 w. D. MAYNARD E 3,509,502

' ELECTROMAGNETIC RELAY STRUCTURE Filed Nov. '2, 19s? .4 Sheets-Sheet 1 FIG. I

INVENTORS W. D. MAYNARD E. A. BELANGER THEIR ATTORNEY April Z8,197O Q w. |v ETAL 3,509,502

ELECTROMAGNETIC RELAY STRUCTURE Filed Nov. '7, 1967 I )4 Sheets-Sheet 2 FIG. 2 FIG. 3

E g 1 5% E 53 Q; E" =5 =E= low 1 =5? 5* L 24 R649 7 p) INVENTORS D. MAYNARD A. BE LANGER THEIR ATTORNEY April 28, 1970 w. p. MAYNARD E- L 3,509,502

ELECTROMAGNETIC RELAY STRUCTURE Filed Nov. 7, 19a"! .4 Shets-Sheet 5 FIG. 4 HG 5 66 7| 10 66 m ig a 3 E35 72 @272 zit- 7'. 18 :1? 3$] 76. 13: E E E E3 E E FIG. 9 |o 113 INVENTORS w. 0. MAYNARD E. A. BELANGER BY W THEIR ATTORNEY April 28, 1970 w. D. MAYNARD EAL ELECTROMAGNETIC RELAY STRUCTURE .4 Sheets-Sheet 4.

Filed Nov. v, 1967 FIG. 8

ME 5 r YR INVENTORS W. D. MAYNARD E. A. BELANGER FIG. 6

THEIR ATTORNEY U.S. Cl. 335-129 11 Claims ABSTRACT OF THE DISCLOSURE This electromagnetic relay is of the safety type as used by railroads. It has parts molded of black fiber glass plastic material and has other parts formed of metal and constructed to be assembled in such a way as to provide a composite structure requiring no adjustment after initial assembly. The armature is mounted on a knife edge bearing with the working airgap at the rear of the relay and the contact operator at the front of the relay. The plastic cover holds a magnetic back yoke in place for connecting the two magnetic core members, which back yoke is directly removable when the cover is removed so as to e able to replace the coils without further disassembly. The coils have quick detachable connectors which connect to the coil lead fingers at the front of the relay. The contact fingers are pushed into position from the front of the relay with the cover removed and a guide block is p rmanently provided for assisting the entry of the contact fingers into the rear mounting block into which such fingers automatically lock when they are placed in position.

BACKGROUND OF THE INVENTION The present invention relates to railroad safety relays, and more particularly to an electromagnetic relay assembled from a multiplicity of parts and constituting an operable relay when once assembled without further adjustment.

Heretofore, electromagnetic relays of the safety type have been built which are highly efficient, but most expensive to manufacture. One of the reasons for the expense in manufacture is that the relay requires a fine adjustment after initial assembly in order to be properly operative. Also, such fine adjustment of the relay tends to deteriorate and reduce the life of the relay.

The present invention relates to a safety type relay which has a gravity biased armature for operating the contacts, which armature is additionally biased by a suitable coil spring so as to minimize its response to vibration and bounce, and also to maintain its operability uniform over a long life. The armature operates the contact fingers of the relay through a contact pusher member connected to the contacts directly in line with their contact points to directly oppose any tendency to stick due to fusion effects that might develop through the relay operation; and also to avoid the variable deflection of the contact fingers.

Thus, the purpose of the present invention is to provide an improved safety relay which does not require adjustment after the initial assembly, and which is easily and rapidly assembled from parts that can be mass produced and yet meet the rigid requirements necessary for safety operations.

Another object of the present invention is to provide an improved relay assembly wherein the parts are readily assembled into precise positions due to the type of manufacture of the parts so as to provide the desired operating "United States Patent characteristics which are insensitive to minor production variations.

A further object of the invention is to provide a relay having an eflicient magnetic structure which can be quickly and readily disassembled in part for the replacement of the coils on the relay.

SUMMARY OF INVENTION In general, the relay of this invention includes a housing structure having the shape of a parallelepiped with rectangular bases, a lattice structure located inside the front of the housing structure and integral therewith, the lattice structure having spaced openings, with a guide block located in the housing structure abutting the lattice structure, and a slotted contact mounting block located within the housing structure at the rear of the guide block, the slots in the contact mounting block being located to match the spaces in the lattice structure, and the guide block having internal chutes with openings at one end matching the spaces in the lattice structure and with openings at the other end matching the slots in the contact mounting block.

The relay of this invention is further characterized by having its housing in the form of a rectangular box substantially open on the inside thereof with openings at the front and back and with the other sides completely enclosed, an electromagnetic structure located in the lower portion of the housing and having an L-shaped armature cooperating therewith, one arm of the armature cooperating with the electromagnet at the rear of the relay to form a working airgap, and the other arm of the armature extending forwardly through the mid portion of the housing, whereby the armature is gravity biased to normally open the working airgap, with electrical contacts mounted in the upper portion of the housing, and a pusher member operated by the other arm of the armature for operating the contacts.

The relay of the present invention is further characterized by having an L-shaped armature mounted on a knife edge bearing in exact alignment with the pole faces of the two cores so as to have one arm of the armature in a working airgap with the pole faces and the other arm eX- tending through the central section of the housing structure and operatively connected to the contacts located in the upper portion of the structure, windings on the two cores, and a slip-on type back yoke having holes for snugly receiving the two cores, and a cover for enclosing the front side of the relay housing with a spring means mounted on the inside thereof for holding the back yoke in position.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings, while its Scope will be pointed out in the appended claims.

In the drawings:

FIG. 1 is a side elevation partially in section taken on lines 1--1 of FIG. 2 which shows the parts of the electro magnetic relay constituting the structure of the present invention;

FIG. 2 is a front view with the cover of the relay removed and with parts shown in section to illustrate the assembly shown in FIG. 1;

FIG. 3 is a back view of the structure shown in FIG. 1 illustrating more particularly the slotted contact mounting block and the coded back cover for the electromagnetic portion of the relay;

FIG. 4 is a front view of the housing structure only of the relay to show the form of the structure to which all of the other parts are related;

FIG. is a side sectional view of the housing structure shown in FIG. 4;

FIG. 6 is an enlarged side view of the armature and its knife edge bearing;

FIG. 7 is an enlarged top view of the armature and its knife edge bearing as shown in FIG. 6;

FIG. 8 shows a front view of the contact pusher member shown in side view in FIG. 1; and

FIG. 9 is a top view of the front cover as mounted on the housing structure and which is held in place on a terminal board by a wire bail fitted over the handle on the cover and extending to the two recesses in the terminal board.

Generally speaking, the electromagnetic relay of the present invention is comprised of a molded frame or housing structure 10 Which encloses the various parts and to which a transparent cover 11 is attached. Inside the upper portion of the housing, the contact assembly is located, and in the lower portion of the housing, the electromagnetic structure is located.

The armature 35 is mounted on a knife edge bearing 31 riveted onto the housing between the upper and lower portions of the housing and near its back. The armature 35 is L-shaped and has a portionor arm which cooperates with the two pole faces 33 and 34 of the two cores 30 which are rigidly attached to the housing structure. There is also a contact operating portion or arm 35A of the armature which extends towards the front of the housing between its upper and lower portions.

The knife edge bearing 31, the armature 35, the cores 30 and the coded back plate 36 are assembled and riveted in place in the housing at the same time on the two vertical bosses 15 located one on each side of the lower portion of the housing. The contact operating portion of the armature 35A rests at its forward end against the upper side of a cross-bridge 18 arranged in the form of an arch connecting the two sides of the housing 10. Also, a flat cross-bridge member 16 is located at the back of the housing connecting the tops of the two vertical bosses 15. There are two horizontal ribs 19 connecting with the two vertical bosses and extending forward to the arched cross-bridge. In a similar fashion, two horizontal ribs 21 extend from the vertical bosses forward to a flat cross-bridge at the front of the housing located between the space allotted to the cores and coil members of the electromagnetic structure.

The first-mentioned flat cross-bridge 16 at the back of the housing and connecting the tops of the two vertical bosses 15- has a downwardly extending abutment 14 running crosswise directly above the armature on its knife edge bearing and acting to hold the armature downwardly on such knife edge bearing.

At the front of the upper portion of the housing is a honeycomb or lattice structure for providing back stops for certain fixed contact fingers and providing supports for the coil springs located to supply the bias to such fixed contact fingers. This honeycomb or lattice also has a back stop for the coil spring which biases the armature to a normal position against the arched crossbridge 18. In addition, this lattice structure provides rigidity to the housing. The back upperportion of the housing is open so as to receive a contact guide block 40 which is also of a honeycomb form. In addition, a rear contact mounting block 42 is provided with suitable slots and is bolted into position following the insertion of the contact guide block 40.

The contact fingers, such as finger 39, are moved into position from the front of the housing. As they enter their respective spaces in the lattice structure at the front of the housing, they also enter the respective chutes, such as chute 44, in the contact guide block which guides the end of the finger to enter the appropriate slot in the contact mounting block 42 at the rear of the relay. As a small portion of this contact 39 extends out of the slot at the rear of the mounting block 42,

a tool is used to grasp the extending end and pull it rearwardly until the contact finger locking member 45 springs downwardly and engages the side of the slot in the block 42. When all the contact fingers are in posi tion, the coil springs 41 are inserted into the lattice structure in a way to bias the fixed contact fingers against their respective stops in the lattice structure. Also, the coil spring 48 for biasing the armature is placed in position in the lattice structure.

Assuming that all of the contact fingers are in appropriate positions, the contact pusher member 51 is mounted over the armature arm 35A and each movable contact finger is inserted in the respective slots in the pusher member 51. When the pusher member 51 is appropriately located, a lock finger 53 is then slipped into position through the slot in the pusher member 51 and through the contact guide block 40 and into the rear contact mounting block 42 until it is locked into position. This lock finger 53 has projections at the front which extend to the right and left as viewed from the front so as to hold the contact pusher member 51 in position against the rear projections on each of the movable contact fingers mounted in the pusher member.

The test fingers 64 are provided with narrow projections at each end. Each finger 64 may he slid into its appropriate position in the slide runways provided at the base of the relay.

The two coils 28 on suitable plastic spools 38 are inserted over the cores 30 and moved into their positions. Their lead wires come out at the front of the relay for attachment to the lead fingers 49 located at the sides of the lattice structure. The quick detachable connectors 50 actually insert through a suitable space in the pusher member 51. When this has been done, a back yoke 62 is fitted onto the two extending cores 30 with such back yoke 62 having holes for receiving the cores which provide a smooth and accurate fit with the core members. The cover 11 is then positioned over the front of the relay to enclose the electromagnetic portion and the contact assembly. A spring 63 is located in the cover to hold the back yoke tightly in position on the cores. The placement of the cover 11 also receives the ends of the test fingers 64 through slots in the cover.

A fiat cross-bridge 69 in the cover .11 fits appropriately just above the winding lead connectors 50 to separate them from the movable contact fingers extending through the contact pusher member. Such cover is held in position by suitable screws inserted into appropriate recessed holes in the corners of the cover and extending into the housing member at its four corners. The relay is then ready to be fitted into a suitable terminal board.

More specifically and with reference to FIG. 1, the electromagnetic relay structure is shown in a side elevational view with certain parts in section as taken in general on lines 1-1 of FIG. 2. This relay comprises a housing structure 10 and a cover member 11. The housing structure 10 is shown with a front view in FIG. 4 with all parts removed and in a side sectional view taken on lines 55 in FIG. 5 also with all parts removed.

Referring to FIG. 4, the housing structure 10 is molded of a fiber glass filled resin in a single piece in the form of a rectangular box-like shape sometimes termed a parallelepiped with rectangular bases. Such molding includes different compartmental separations and structure to give added strength and rigidity to the structure, as well as providing certain functions broadly explained above.

In FIGS. 4 and 5, it can be seen that the housing struc ture 10 has inwardly extending vertical bosses 15 along the rear inside edge on both sides. At the top of these bosses 15 is a cross-bridge 16 which is flat and extends between the two sides of the housing 10. An upstanding central boss 17 is provided for receiving a screw. Around the inside of the wall of the housing 10 adjacent the rear edge is a depressed strip making the wall of the housing slightly thinner. This makes a recess for receiving the slotted contact mounting block 42. This block 42 has screws inserted in the boss 17 at the bottom of the upper space or portion and also inserted in the two bosses 66 at the top (see FIG. 4). Therefore, the top fioor of the cross-bridge 16 is raised slightly on each side of the boss 17; and similarly the underside of the same portion is slightly raised. The abutment 14 joins these two levels underneath and extends downwardly an appropriate amount to meet the top of the armature. In FIG. 4, it can be seen that the lower edge of the abutment 14 is very slightly curved downwardly (see thick line) in the center just a sufiicient amount to just barely clear the armature. This allows the armature to ride flat on its knife edge bearing 31 without binding as seen in FIG. 1, and yet be properly held in position.

At the front of the housing is an arched cross-bridge 18 which extends from side to side. Running along each side of the housing 10 on the inside are ribs 19. Each of these ribs 19 connects the arched cross-bridge 18 with the corresponding vertical boss on its side of the housing. To give added strength, the ribs 19 have raised edges near the front and leading into the sides of the upper floor of the arched cross bridge 18 as best seen in FIG. 5.

Another flat cross-bridge 20 connects the sides of the housing 10 at the front thereof, and this cross-bridge 20 also has ribs 21 extending backwardly along the sides to the corresponding vertical bosses 15.

At the bottom of the housing 10 is a compartment for receiving the test fingers 64 which compartment is provided with the enclosing flat bridge 22 located at the bottom of the vertical boss 15. A vertical rib 23 near the center of the compartment runs the length of it to give stability. Similar ribs 29 are located at each side of the compartment for the same reason. Within the two smaller compartments are pairs of grooved ribs 24, 25 and 26. At the back of this lower compartment, located a short distance inwardly is a horizontal enclosing rib 27 having these vertical slots seen in FIG. 4.

The upper portion of the housing structure 10 is a honeycomb or lattice structure which forms the back stops 70 for the fixed contacts and also the seats 71 for the coil springs biasing such contacts. Spaces 72 are also provided for the movement of the movable contacts. At the bottom of this honeycomb there are two grooved spaces 73 for receiving pairs of coil connector fingers. A seat 75 is also provided for the armature biasing coil spring 48. In the four corners of the housing 10 are bosses for receiving self-tapping screws adapted to secure the cover 11 in place.

The inside of the honeycomb or lattice structure has two further inwardly projecting ribs 76'for giving added strength to the lattice structure and also for limiting the inward position of the contact guide block 40. These two ribs 76 extend downwardly from the top of the housing 10 to the slot 77. An intermediate slot 78 'also connects the two vertical ribs 76 which are in line from the front of the lattice structure to the near mid portion of the contact compartment.

With the above general understanding of the housing structure, it can be readily seen that the cores 30 can have their pole pieces 33 and 34 fitted into recesses in the vertical bosses 15. Also, a knife edge bearing plate 31 can be placed in the recess between thecross-bridge 16 and the ribs 19, so as to receive the armature 35. The coded back plate 36 is placed over the compartment and rivets 37 are slipped through the pole pieces 33 and 34, the bosses 15 and the coding plate 36. The flattening of the heads of these rivets 37 thus secure the core pieces 30, the armature and its bearing 31, the coded back plate 36 in position. The core pieces 30 thus extend outwardly toward the front of the housing 10. The armature 35 has two vertical slots, one on each side, which are slightly wider than the bearing strip 31 (see FIG. 6). The position shown in FIG. 6 is with the armature in its attracted position at which time the armature lays flat against the flat plastic residual strips on the pole faces. Such strips are placed on the pole faces just before they are fitted into the vertical bosses 15. With the armature in this position, the entire slot of the armature is required for the sides of the bearing which merely enter the slots which is best seen in FIG. 7. The right-hand side of the bearing plate is in exact alignment with the left side of the armature. The coil button 46 is also slipped into its receiving hole in the armature 35A.

The contact guide block 40 is slipped into the upper portion of the housing structure 10 and is held in position against the back of the lattice structure by placing the contact mounting block 42 in position where it is held by inserting three self-tapping screws 43.

The fixed contact fingers 39 are slid into appropriate spaces in the lattice structure and enter the contact guide chute 44 in the contact guide block 40. Upon the further insertion of the contact, it is guided to enter its slot in the mounting block 42. When a sufiicient portion of the finger exits through the slot in the block 42, a tool is inserted into the recess at the rear of block 42 adjacent the slot and is used to pull it through until the lock finger 45 springs downwardly and holds the contact in place. This fit of the contact 39 in the block 42 is snug and tight on both the upper and lower surfaces of the contact and particularly so with regard to the side edges. It is the snug slot in this block plus the continuing longitudinal sliding portions into the block which determine the relatively exact perpendicular projection of the forward end of the contact finger 39. When the fixed contacts are positioned, then the movable contacts 59 are similarly slid into their positions where they lock in place. When all of these contacts are in position, suitable coil springs 41 are placed on their seats in the lattice structure for biasing the fixed contacts to their appropriate normal positions. In addition, insulated seat 46 is inserted into a hole 47 in the armature and a biasing spring 48 slipped into position onto the two opposing seats 46 and 75.

The winding connector fingers 49 are slipped into position the same as the other contact fingers, but these contact fingers merely extend forwardly for receiving quick detachable connectors 50.

When all of the fingers have been placed in position, the contact pusher member 51 shown in front view of FIG. 8 is positioned over the armature arm 35A and gently laid against the movable contacts which may need slight adjustment in order to enter the slots in the extending fingers 91 and 92 of the contact pusher member. These fingers 91 and 92 grasp each of the movable contacts exactly opposite their contact making points so that such contacts are forceably moved by operation of the armature removing any tendency of the contacts to burn closed as the pusher member 51 is moved by the armature.

When the pusher member 51 is moved inwardly so that it abuts against the contact side extensions, then a lock finger 53 is inserted which has projections at its outer end for holding the pusher member 51 in position. This lock finger 53 has the same kind of locking fingers 45 for the contact block 42 as previously described.

The coils are wound on plastic spools 38 which readily slide over the core members 30 with the coil ends suitably positioned and having the quick detachable contact members 50 attached at their ends. Thus, the two coils can be slipped over their respective cores 30 and their four terminals suitably connected to their respective fingers 49 rather quickly through appropriate spaces left in the contact pusher member 51. The outer ends of the spools 38 have a raised portion at one side. These raised portions are placed at the top and the bottom of their respective spools so that a back yoke 62 can he slipped over the ends of the cores. This fit of the back yoke 62 is snug so as to make ready magnetic contact with the cores 30. This back yoke 62 is molded from powdered magnetic material which is amalgamated into a unitary structure which has high magnetic permeability.

A spring 63 is located in a suitable space on the cover for contacting the back yoke 62 and holds it firmly in position, when the cover is placed in position. The test fingers 64 may have to be slightly adjusted to enter their respective slots in the cover.

When the cover is in position, the screws 65 are inserted to hold the cover 11 onto the housing 10. When the relay is thus constructed, it is complete and ready for operation.

To place it in operation, it is merely mounted on a plug board adapted to receive its projecting contact fingers and having coded projections to enter the coded holes in the coded back cover 36. A wire bail 60 is connected in the slot on the terminal board and is sprung over the outer handles'81 of the relay as shown in FIG. 9. In this way the relay is held on the terminal board and is removable when desired.

It is noted that FIG. 8 shows an enlarged front view of pusher member 51 which can also be found in FIGS. 1 and 2. This front view shows the extending lips 91 and 92 which take hold of the contact fingers directly adjacent the contact points as can also be seen in FIGS. 1 and 2. Also, mild shading is shown in areas of FIG. 8 to illustrate the thin webs 93 of molded material between major portions or bars of the material. These thin web portions 93 act to give strength and stability to the pusher member 51. The larger fingers 94 act to grasp the armature arm 35A as can be seen in FIG. 2. (It is noted that one of these fingers 94 is omitted from FIG. 2.)

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein, without departing from the invention; and, it is, therefore, intended that the appended claims shall cover all such changes and modifications as fall within the true spread and scope of the invention.

What we claim is:

'1. An electromagnetic relay having a plurality of contacts wherein the improvement comprises a rectangular box shaped housing substantially open on the inside thereof with openings at the front and back and with the other sides completely enclosed, an electromagnetic structure located in the lower portion of said housing and having an L-shaped armature cooperating therewith, one arm of said armature cooperating with said electromagnet at the rear of the relay to form a working airgap, and the other arm of said armature extending forwardly through the mid portion of said housing, whereby said armature is gravity biased to normally open said working airgap, electrical contacts mounted in the upper portion of said housing, and a pusher member operated by said other arm of said armature for operating said contacts, the housing having formed integral therewith at the front of the relay a lattice structure for supporting one end of the contacts that are fixed in that they are not subject to actuation by the armature.

2. A relay according to claim 1 in which a lattice structure is located in the upper portion of said housing with said electrical contacts mounted therein, and a coil spring mounted between said lattice structure and said armature for additionally biasing said armature.

3. A relay according to claim 1 in which said armature is mounted on a knife-edge bearing near its center, which is secured to the housing and in which the housing has a cross-bridge with an underhanging abutment directly over said armature above said knife-edge bearing.

4. A relay according to claim 1 in which said armature is mounted on a knife-edge bearing near its center, which is secured to the housing and in which the housing has a cross-bridge between the sides of said housing above said bearing and having an underhanging abutment, said abutment having a very slight arcuate portion across said armature and barely failing to touch said armature at its center.

5. A relay according to claim 1 in which said forward end of said armature is supported by an arched bridge portion of the housing connecting the two sides of said housing.

6. A relay according to claim 1 in which said forward end of said armature in its released position is supported by an arched cross-bridge member connected between the sides of said housing, and a coil spring between said armature and another cross-bridge member for biasing said armature toward said arched crossbridge.

7. In a relay, a housing structure of rectangular box shape and generally open on the inside thereof, the front and back portions of said structure being substantially open and the other sides thereof being completely enclosed, electrical contacts mounted in the upper portion of said structure and an electromagnet in the lower portion of said structure and having two cores with parallel pole faces at the back thereof, an L-shaped armature mounted on a knife-edge bearing in alignment with said pole faces so as to have one arm of said armature in a working airgap with said pole faces and the other arm extending through the central portion of said structure and operatively connected to said contacts, windings on said two cores, and a slip-on type back yoke having holes for snugly receiving said two cores, and a cover for enclosing the front side of said relay with a spring means mounted thereon for holding said back yoke in position.

8. In a relay as specified in the claim 7 wherein said windings have extending coil connections with quick detachable connectors mounted thereon, said quick detachable connectors being connected to coil connector fingers running fromfront to the back of said relay.

9. In a relay: structure as specified in claim 7 wherein there are bosses running vertically along the back edge of the lower portion of said housing structure, and wherein said core members are mounted on the front of said bosses and a coded back plate is mounted at the rear of said relay on said bosses and said core and 'back plate being riveted to said bosses by the same rivets, said coded back plate having holes arranged in a coded configuration.

10. In a relay structure as specified in claim 7 wherein a spaced compartment is located at the bottom of the relay having grooved ridges running through an enclosed space for receiving test fingers each having constricted projections at each end, the projections at one end for passing through slots at the rear end of said compartment and the projections at the other end for passing through slots in said cover.

11. In a relay, a rectangular box shaped housing substantially open on the inside thereof with openings at the front and back and with the other sides completely enclosed, said housing being molded of a fire resistant plastic resin, and having a lattice framework in the upper front of the structure with cross members and with spaces, a slotted contact mounting block located within said housing at the rear thereof, said slots being located to match the spaces in said lattice framework, fixed and movable contact fingers mounted in said slots of said contact mounting block and extending through said lattice framework, an electromagnetic structure located in the lower portion of said housing and having an L-shaped armature cooperating therewith, said armature having one arm cooperating with said electromagnet at the rear of the relay to form a working airgap, and the other arm of said armature extending forwardly through the mid portion of said housing, a pusher member operated by said other arm of said armature and connected to said movable contacts, coil springs mounted in said lattice work for holding said fixed contacts against their respective cross members, and a coil spring between said lattice work and said armature for biasing said armature to open said working airgap, said core structure extending forward in the relay and having mounted thereon energizable coils, a sintered back yoke snugly fitted over said core members but removable therefrom, and a cover for enclosing the front 9 10 side of said relay with a spring means mounted thereon 3,076,880 2/1963 Ehrismann 335128 for holding said back yo ke in position. 3,270,301 8/1966 Bengtsson 335-129 References Cited BERNARD A. GILHEANY, Primary Examiner UNITED STATE P TEN 5 H. BROOME, Assistant Examiner 990,032 4/1911 Clement 335128 2,134,448 10/1938 Knos 335-129 5 2 2 2,556,716 6/1951 Viol 335-129 33 0 3,001,049 9/1961 Didier 335-136

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